<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body{

        }
        #app{
            width: 600px;
            height: 400px;
            background-image:url("../img/1.jpg");
            background-size: 100% 100%;
            margin: auto auto;
        }

    </style>
</head>
<body>
<div id="app">

</div>
</body>
</html>